The Effect of Cycloplegia on Ocular Alignment and AC/A Ratio.

Purpose: The present study sets out to investigate the effect of cyclopentolate-induced cycloplegia on distance and near deviation and the accommodative convergence/accommodation (AC/A) ratio. Methods: This prospective study was performed on 30 subjects. The inclusion criteria included a lack of any active ocular pathology and systemic diseases, no history of ocular surgery, and nonuse of various medications. Refraction, near and distance deviation were measured for all subjects, and the same examinations were repeated after the administration of two drops of cyclopentolate 1% to both eyes. Results: The obtained data from 30 subjects, including 19 males, with a mean age of 22.53 ± 1.74 years were analyzed. The mean ± SD of near deviation in dry and cycloplegic conditions were -6.9 ± 8.1 and +6.4 ± 9.1 prism diopters, respectively, which were statistically significant (P < 0.001). Distance deviation in cycloplegic conditions demonstrated an average difference of 0.8 prism diopters, compared to dry conditions (P < 0.001). AC/A ratios were 4.7 ± 2.5 and 9.7 ± 3.9 (Δ/D) in non-cycloplegic and cycloplegic conditions, respectively, which was a statistically significant difference (P < 0.001). The multiple regression indicated that among all under study variables, refraction (B coefficient: -2.4; P < 0.001) and near pre-cycloplegic deviation (B coefficient: 0.56; P < 0.001) were significantly associated with post-cycloplegic near deviation. Conclusion: The results of this study indicated that cycloplegia causes a considerable esophoric shift in near deviation and a negligible esophoric shift in distance deviation. As a result, the AC/A ratio demonstrated a significant increase due to unequal changes in near and distance deviation.

Receded near point of convergence as a predictor of mild cognitive impairment in the general geriatric population: results from a population-based study.

AIM: To investigate the relationship between near point of convergence (NPC) and mild cognitive impairment (MCI) in the general elderly population. METHODS: The present report is a part of the Tehran Geriatric Eye Study (TGES): a population-based cross-sectional study conducted on individuals 60 years of age and above living in Tehran, Iran using the multi-stage stratified random cluster sampling method. Cognitive status was assessed using the Persian version of the Mini-Mental State Examination (MMSE). All study participants underwent complete ocular examination including measurement of uncorrected and best-corrected visual acuity, objective and subjective refraction, cover testing, NPC measurement, and slit-lamp biomicroscopy. RESULTS: The data of 1190 individuals were analyzed for this report. The mean age of the participants analyzed was 66.82±5.42 (60-92y) and 728 (61.2%) of them were female. Patients with MCI had a significantly more receded NPC compared to subjects with normal cognitive status (10.89±3.58 vs 7.76±2.71 cm, P<0.001). In the multivariable logistic regression model and in the presence of confounding variables, a receded NPC was statistically significantly associated with an increased risk of MCI (odds ratio: 1.334, 95% confidence interval: 1.263 to 1.410, P<0.001). According to receiver operating characteristic (ROC) analysis, a cut point NPC> 8.5 cm (area under the curve: 0.764, P<0.001) could predict the presence of MCI with a sensitivity and specificity of 70.9% and 69.5%, respectively. CONCLUSION: A receded NPC can be clinically proposed as a predictor of MCI in older adults. It is recommended that elderly with a receded NPC>8.50 cm undergo detailed cognitive screening for a definite diagnosis of MCI. In this case, the necessary interventions can be carried out to slow down MCI progression to dementia.

Anterior and posterior corneal higher-order aberrations in early diagnosis and grading of keratoconus.

CLINICAL RELEVANCE: Evaluation of corneal higher-order aberrations can be used clinically to diagnose early cases of keratoconus as well as to classify the severity of keratoconus. BACKGROUND: To investigate the anterior and posterior corneal higher-order aberrations (HOAs) up to the sixth order and their ability to identify early keratoconus (KCN) as well as differentiate different severities of KCN using cross-validation analysis. METHODS: This prospective cross-sectional comparative study was performed at a tertiary eye hospital in Tehran, Iran, in 2019. The study sample consisted of 95 eyes of 95 patients with KCN and 53 eyes of 53 normal individuals. The eyes with KCN were classified into three groups based on the Amsler-Krumeich classification system: group 1 (mild KCN), group 2 (moderate KCN), and group 3 (severe KCN). Corneal wavefront analysis was performed using Pentacam HR. RESULTS: Based on the magnitude of AUC, posterior vertical secondary coma (Z5-1) had an excellent discriminant ability (AUC: 0.91) and anterior vertical coma (Z3-1) and anterior vertical secondary coma (Z5-1) had a good discriminant ability (0.8 < AUC < 0.89) for differentiating eyes with mild KCN from normal eyes. The anterior and posterior primary spherical aberrations (Z4°) had an excellent ability (AUC > 0.9), and anterior secondary spherical aberration (Z6°) had a good ability (AUC: 0.83) for differentiating moderate from mild KCN. In the differentiation of severe from moderate KCN, anterior and posterior primary aspherical aberrations (Z4°) had a good AUC value (AUC > 0.8). CONCLUSION: Coma-like aberrations had a good discriminant ability between normal eyes and eyes with mild KCN. Spherical aberrations showed a good ability for differentiating between different stages of KCN. The cut-off values reported in this study can be used for early detection of KCN as well as classification of KCN severity.

Binocular Function in Different Gaze Positions.

Purpose: To evaluate varied aspects of binocular function in multiple gaze positions. Methods: In 2018, this cross-sectional study was conducted on 21 participants (male = 11) with an age range of 19-25 years. Having emmetropia and 10/10 visual acuity in both eyes were conditions of the inclusion criteria for the cross-sectional study. The following aspects of binocular function including amplitude of accommodation (AA), near point of convergence, near phoria, and monocular accommodative facility were evaluated in five gazes (primary, upward, downward, left, and right) for all subjects. Results: Near point of convergence values showed significant differences in all gaze positions (P < 0.001). The lowest near point of convergence value was seen in the primary gaze (2.69 cm) and the downward gaze (3.47 cm) and the highest near point of convergence value was seen in the left gaze (7.5 cm). There was also a significant difference in the amplitude of accommodation among the upward, downward, and the primary gaze (P < 0.001) positions but no difference was observed among the temporal, nasal, and the primary gaze positions. There was a significant difference in near phoria between the upward gaze and the primary gaze (P = 0.008) while no significant differences were observed among the other gazes. There was no significant variance in the monocular accommodative facility among the different gaze positions (P = 0.175). Conclusion: The results of this study indicated variations that exist in the convergence and accommodation reflex functions in multiple gaze positions, which proved to be more prominent in the convergence system. Although the accommodative sufficiency evaluation was inconsistent among the multiple gaze positions, the accommodative facility evaluation was consistent in all gazes.

Assessing Accuracy of Okulix Ray-Tracing Software in Calculating Intraocular Lens Power in the Long Cataractous Eyes.

Purpose: To investigate the accuracy of Okulix ray-tracing software in calculating intraocular lens (IOL) power in the long cataractous eyes and comparing the results with those obtained from Kane, Holladay 1 with optimized constant, SRK/T with optimized constant, Haigis with optimized constant, and Barret Universal 2 formulas. Methods: The present study evaluates the refractive results of cataract surgery in 85 eyes with axial length > 25 mm and no history of ocular surgery and corneal pathology. IOL power calculation was performed using the Okulix software. The performances of Okulix software in comparison with the five other formulas were evaluated by predicted error, mean absolute error, and mean numerical error 6 months after surgery. Results: The mean calculated IOL power by the Okulix software was +13.48 ± 4.19 diopter (D). The mean of the 6-month postoperative sphere and spherical equivalent were +0.18 ± 0.63 and -0.34 ± 0.78 D, respectively. Also, the 6-month spherical equivalent in 56.6% and 80% of eyes were within ±0.05 and ±1.00 D, respectively. The predicted error (P < 0.001) and the mean numerical error (P < 0.001) were different between the six studied methods; however, we were not able to find any significant differences in the mean absolute error among six studied methods (P: 0.211). Conclusion: The present study showed acceptable performance of the Okulix software in IOL power calculation in long eyes in comparison with the other five methods based on the postoperative refractive error, calculated mean absolute error, and mean numerical error.

The Prevalence of Fusional Vergence Dysfunction in a Population in Iran.

PURPOSE: To determine the prevalence of fusional vergence dysfunction (FVD) and its relationship with age, sex, and refractive errors in a population-based study. METHODS: In this cross-sectional study, all residents of Mashhad, northeast of Iran, aged >1 year were subjected to random stratified cluster sampling. After selecting the participants, they all underwent complete optometric examinations including the measurement of visual acuity and refraction, assessment of binocular vision and accommodative status, and slit-lamp biomicroscopy. RESULTS: Of 4453 invited individuals, 3132 participated in the study. After applying the exclusion criteria, statistical analysis was performed on the data of 1683 participants. The prevalence of FVD was 3.2% in all participants, 4.0% in men, and 2.9% in women (P = 0.234). The prevalence of FVD increased linearly with aging from 2.3% in the age group of 10-19 years to 5.4% in the age group of 40-49 years (P = 0.034). The prevalence of myopia, hyperopia, and emmetropia was 11.1%, 29.6%, and 59.3% in participants with FVD and 16.7%, 26.4%, and 57% in participants without FVD, respectively (P = 0.570). Multiple logistic regression analysis only showed a significant association between age and FVD (odds ratio =1.03 95% confidence interval: 1.02-1.05, P = 0.031). CONCLUSION: The prevalence of FVD in this study was higher than most previous reports and increased significantly with aging. FVD had no significant association with sex and refractive errors.

Evaluating Reading Performance in Different Preferred Retinal Loci in Persian-Speaking Patients with Age-Related Macular Degeneration.

PURPOSE: To evaluate reading performance in different preferred retinal loci (PRLs) using a Persian version of a Minnesota Low Vision Reading (MNREAD) chart in Persian-speaking patients with age-related macular degeneration (AMD). METHODS: In this cross-sectional study, 35 patients with AMD were assessed. The reading performance was investigated by the MNREAD chart without using low vision aids. The location of PRL was determined monocularly using an MP1 microperimeter (Nidek Technologies, Padua, Italy). The anatomical location of the fovea was determined using optical coherence tomography (OCT). Images were taken with the MP1 microperimeter, and Spectralis HRA-OCT device was processed using graphic software to determine the location of the PRL on the retina. RESULTS: Thirty-five patients (51 eyes) with a mean age of 73.8 ± 7.7 years (range, 54-88 years) were assessed. Mean best corrected distance visual acuity (logMAR) was 0.65 ± 0.35 (range, 0.2-1.3). Mean levels of reading acuity (RA) (P = 0.009) and critical print size (CPS) (P = 0.015) were significantly different in different locations of PRL. Average scores of maximum reading speed (MRS) (P = 0.058) and reading accessibility index (ACC) (P = 0.058) were not statistically significant in different locations of PRL. There was a positive correlation between PRL-fovea distance and RA (P < 0.001, r = 0.591) and CPS (P < 0.001, r = 0.614). Significant negative correlations were observed between PRL-fovea distance and MRS (P < 0.001, r = -0.519) and ACC (P < 0.001, r = -0.545). CONCLUSIONS: This study provides evidence for differences in the reading performance of Persian-speaking patients with AMD in different PRL locations. The average scores of all reading indices obtained in the right-field PRL are lower than those in other areas and are highly correlated with the PRL-fovea distance.

Evaluation of the presence of a central fusion lock effect on fixation disparity curve parameters in symptomatic and asymptomatic subjects.

Clinical relevance: Several parameters are likely to affect the magnitude of fixation disparity (FD) and FD curve characteristics. Presence of a central fusion lock may have an important effect on clinical testing of FD and interpretation of its results.Background: The aim of this study was to evaluate FD curve parameters using the modified near Mallett unit (with a central fusion lock) and the Sheedy disparometer (without a central fusion lock) in symptomatic and asymptomatic subjects.Methods: This cross-sectional study was conducted in 147 patients with a mean age of 22.5 years who presented to the optometry clinic of Paramedical College of Mashhad University of Medical Sciences. The symptoms were recorded in a questionnaire for each patient. FD was measured using the modified near Mallett unit and Sheedy disparometer and FD curves were generated using the AutoCAD 2005 software.Results: There was a significant difference in the FD, associated phoria, and slope measurements between the two devices (all p values < 0.05). Significant difference was found in the mean FD between symptomatic and asymptomatic subjects using the modified near Mallett unit (p < 0.0001) and Sheey disparometer (p = 0.007). In symptomatic subjects, the mean slope was steeper for the modified near Mallett unit compared to the Sheedy disparometer (p = 0.001). Although the mean centre of symmetry was more negative in the modified near Mallett unit versus the Sheedy disparometer, the difference between the instruments was not significant in symptomatic (p = 0.477) and asymptomatic (p = 0.257) participants.Conclusion: There are differences in the FD curve parameters between the modified near Mallett unit and Sheedy disparometer. Slope is a proper criterion for differentiating asymptomatic subjects from symptomatic individuals. The modified near Mallett unit is a more precise tool for assessment of non-compensated heterophoria compared to the Sheedy disparometer.

Location and stability of the preferred retinal locus in native Persian-speaking patients with age-related macular degeneration.

CLINICAL RELEVANCE: The findings of this study can be used in the selection of the preferred retinal locus to establish better rehabilitation services such as eccentric viewing training for patients with age-related macular degeneration. BACKGROUND: The aim of this study was to determine the characteristics of the preferred retinal locus in native Persian-speaking patients with age-related macular degeneration. METHODS: In this non-interventional case series, all patients with a diagnosis of age-related macular degeneration referred to the Retina Clinic of the Rassoul Akram Hospital, Tehran, Iran, were evaluated. The fixation characteristics were evaluated monocularly using the MP1 microperimeter (Nidek Technologies, Padua, Italy). Optical coherence tomography was used to determine the location of the central fovea. The images were overlaid and the preferred retinal locus-fovea distance was measured using Image J software. RESULTS: Fifty-one eyes of 35 patients with a mean age of 73.8 ± 7.7-years were evaluated in this study. Inferior-field, left-field, central-field, right-field, and superior-field preferred retinal locus were detected in 49 per cent, 33.3 per cent, 7.8 per cent, 5.9 per cent, and 3.9 per cent of the subjects, respectively. Fixation was stable in 70.6 per cent, relatively unstable in 15.7 per cent, and unstable in 13.7 per cent of the participants. Significant differences were not found in the mean values of logMAR visual acuity between different fields of the preferred retinal locus after Bonferroni correction (p = 0.031). Analysis of co-variance showed no significant difference in mean sensitivity values between different locations of the preferred retinal locus (p = 0.07). The mean preferred retinal locus-fovea distance was not significantly different between different fields of the preferred retinal locus (p = 0.063). CONCLUSIONS: Native Persian-speaking patients with central scotoma secondary to age-related macular degeneration place their self-selected preferred retinal locus most frequently in the inferior and left visual field, which would result in scotoma displacement to the superior and right visual field. Fixation stability was statistically similar in different locations of preferred retinal locus, but it improved with decreasing the preferred retinal locus-fovea distance.

Economic Inequality in Unmet Refractive Error Need in Deprived Rural Population of Iran.

PURPOSE: To determine economic inequality in unmet refractive error (RE) need and its determinants in deprived rural population of Iran. METHODS: In this population-based study, two villages were randomly selected from among underserved villages of Iran. After selecting the participants, optometric examinations, including uncorrected and corrected visual acuity and subjective and manifest refraction, were done for all the participants. Then, unmet need for glasses was determined. Concentration index (C) was used to assess inequality, and Oaxaca-Blinder decomposition method was applied to decompose the gap between the two groups based on the determinants. RESULTS: Of 3851 samples, 3314 participated in the study (response rate = 86.05%). The data of 3255 participants were used for analysis. The value of C and 95% confidence interval (CI) was -0.088 (-0.157 to -0.020), indicating a pro-poor inequality in unmet need. The prevalence (95% CI) of unmet need was 11.74% (9.25-14.22) in the poor and 6.51% (4.96-8.06) in the rich, with a gap of about 5% in favor of the rich (P < 0.001). A marked percentage of the gap was due to the explained portion (b = 5.73; P = 0.031). In the explained portion, the variable of economic status (b = 3.48; P = 0.004) and myopia (b = 0.88; P = 0.031) caused inequality in favor of the rich and against the poor, respectively. In the unexplained portion (b = -0.51; P = 0.372), the variables of education (P = 0.002) and place (P = 0.001) had statistically significant effects on inequality. CONCLUSIONS: There is a significant pro-poor economic inequality in the prevalence of unmet need in rural areas of Iran. Although part of this inequality is related to variables such as education and myopia, a major portion (two thirds) of this inequality may be due to the direct effect of economic inequality.

Demographic profile, clinical, and topographic characteristics of keratoconus patients attending at a tertiary eye center.

PURPOSE: To evaluate the demographic profile, clinical, and topographic characteristics of keratoconus (KCN) patients attending at a subspecialty eye hospital in Tehran, Iran. METHODS: In this cross-sectional study, all patients who attended Noor Eye Hospital between March 2011 and March 2017 and had a diagnosis of KCN were identified, and the required number of patients was randomly selected. The following data were extracted from patient's records: age, sex, visual acuity, refraction, keratometry, pachymetry, and treatment procedures. The data of KCN laterality, severity, morphology, and cone location were also extracted by analyzing the corneal imaging maps. RESULTS: The records of 1080 eyes of 540 patients were evaluated. The mean age of the participants was 31.04 ± 8.54 years (range, 13-63 years), and 69.3% of the patients were male. The highest and lowest frequency of KCN was seen in the age group 20-30 years and above 50 years, respectively. Bilateral KCN was detected in 93.3% [95% confidence interval (CI): 91.68-94.75] of the subjects. 43.7% (95%CI: 32.88-54.48), 55.6% (95%CI: 44.73-66.38), and 0.8% (95%CI: 0.75-0.78) of the cases had nipple, oval, and globus cones, respectively. The cone was central in 52.1% (95%CI: 41.10-63.11), paracentral in 43.6% (95%CI: 36.13-51.04), and peripheral in 4.3% (95%CI: 00.76-7.86) of the cases. The frequency percentage of KCN according to severity was 15.2% (95%CI: 13.09-17.46), 56.4% (95%CI: 53.37-59.37), and 28.4% (95%CI: 25.75-31.21) for mild, moderate, and severe KCN, respectively. Among different parameters, only cone location had a significant association with age as the frequency of paracentral and peripheral cones increased with ageing (P = 0.002). CONCLUSIONS: The mean age of KCN patients in our study was higher than similar studies in other Asian countries. KCN was bilateral in most cases with an oval morphology and central cone location. Most of the patients had moderate to severe KCN.

Are the results of handheld auto-refractometer as valid as the result of table-mounted refractometer?

PURPOSE: To determine the agreement of table-mounted and handheld auto-refractometers and to evaluate the effect of age and different types of refractive errors on this comparison. METHODS: In this cross-sectional study conducted in 2015 using multi-stage cluster sampling, two underserved villages were selected randomly in the north and southwest of Iran. All the selected participants underwent optometric and ophthalmic examinations. Refraction was measured using handheld and table-mounted auto-refractometers in 652 subjects. RESULTS: The mean age of the subjects was 32.7 ± 18.72 years, and 58.3% of them were female. A significant difference was observed in the results of sphere, spherical equivalent (SE), and J45 vector between the two devices (P < 0.012), but there was no significant difference in J0 vector. There was a significant difference in the results of sphere between the two devices in all age groups under 50 years (P = 0.005), but there was no difference in age groups above 50 years. Correlation coefficients of the two devices were 0.989, 0.986, 0.908, and 0.951 for the results of sphere, SE, J0 vector, and J45 vector, respectively (P < 0.0001). The 95% limit of agreement (LOA) of the two devices was -0.31 to +0.53 for sphere, -0.27 to +0.63 for SE, -0.27 to +0.27 for J0 vector, and -0.16 to -0.17 for J45 vector. CONCLUSIONS: According to our findings, the spherical error and cylindrical power measurements of the two devices have a significant correlation. Although there is a significant difference in the mean values between the two devices, this difference may be considered clinically insignificant, and considering the narrow 95% LOA between the two devices, the results may be used interchangeably.

Accommodative insufficiency in a student population in Iran / Insuficiencia acomodativa en una población estudiantil de Irán

Purpose: To determine the prevalence of accommodative insufficiency (AI) and its relation with age, gender, and refractive errors in a college-age student population in Iran. Methods: The present study was conducted cross-sectionally in 2017. All students had optometric tests including measurement of visual acuity, objective and subjective refraction, as well as binocular vision and accommodative examinations. Amplitude of accommodation was measured with the Donders¡' push-up method using the Royal Air Force (RAF) rule. Monocular accommodative facility was measured with ±2.00 diopter flipper lenses. The accommodative response was tested using dynamic retinoscopy with the monocular estimation method (MEM). Results: The prevalence of AI in the studied population was 4.07% (95% CI: 2.61-5.52). The rate was 6.04% (95% CI: 3.58-8.50) in females and 2.01% (95% CI: 0.53-3.48) in males, and logistic regression showed a significantly higher odds of AI in females (OR = 3.14, 95% CI: 1.33-7.45, p-value = 0.009). The prevalence of AI was 2.59% (95% CI: 0.55-7.56) in the 18-19-year-old age group and 4.08% (95% CI: 0.09-8.07) in the 24-25-year-old group (p-value = 0.848). The prevalence of AI among emmetropic, myopic, and hyperopic individuals was 3.74% (95% CI: 1.88-5.61), 4.44% (95% CI: 2.07-6.81), and 5.26% (95% CI: 4.79-16.32), respectively (p-value = 0.869). In the multiple regression model, only gender showed significant relationship with AI (Odds ratio = 3.14, 95% CI: 1.33-7.45; p-values = 0.009). Conclusion: The prevalence of AI in the present study is lower than the most prevalence rates reported in previous studies. In the present study, gender and AI showed a strong association, such that AI prevalence was significantly higher in females than males

Objetivo: Determinar la prevalencia de la insuficiencia acomodativa (IA) y su relación con la edad, sexo, y errores refractivos en una población universitaria de Irán. Métodos: El presente estudio se realizó de forma transversal en 2017. Se realizaron pruebas optométricas a todos los estudiantes, incluyendo medición de la agudeza visual, refracción objetiva y subjetiva, visión binocular y pruebas de acomodación. La amplitud de acomodación se midió con el método de Donders (push-up) utilizando la regla de la RAF (Royal Air Force). La flexibilidad acomodativa monocular se midió con flippers de ± 2 dioptrías. La respuesta acomodativa se evaluó mediante retinoscopía dinámica utilizando el método de estimación monocular (MEM). Resultados: La prevalencia de IA en la población de estudiantes fue de 4,07% (95%ICI: 2,61-5,52). La tasa fue de 6,04% (95%IC: 3,58-8,5) en mujeres y 2,01% (95%IC: 0,53-3,48) en varones, y la regresión logística reflejó un odds ratio significativamente superior de IA en mujeres (OR= 3,14, 95%IC: 1,33-7,45, valor p = 0,009). La prevalencia de IA fue de 2,59% (95%IC: 0,55-7,56) en el grupo de edad de 18-19 años, y de 4,08% (95%IC: 0,09-8,07) en el grupo de 24-25 años (valor p = 0,848). La prevalencia de IA entre los individuos emetrópicos, miopes e hipermétropes fue de 3,74% (95%IC: 1,88-5,61), 4,44% (95%IC: 2,07-6,81), y 5,26% (95%IC: 4,79-16,32), respectivamente (valor p=0,869). En el modelo de regresión múltiple, únicamente el sexo reflejó una relación con IA (Odds ratio = 3,14 95%IC: 1,33-7,45; valor p= 0,009). Conclusión: La prevalencia de IA en el presente estudio es inferior a la mayoría de las tasas de prevalencia reportadas en estudios previos. En el presente estudio, sexo e IA reflejaron una fuerte asociación, en el sentido de que la prevalencia de IA fue significativamente superior en las mujeres con respecto a los varones

Time-course investigation of postural sway variability: Does anxiety exacerbate the sensory reweighting impairment in chronic stroke survivors?

Although anxiety is one of the most prevalent psychological disorders in stroke survivors, its effect on sensory reweighting has not yet been fully studied. The aim of this work was to investigate how anticipation of collision avoidance events affects sensory reweighting in chronic stroke survivors with low and high levels of anxiety (LA-stroke and HA-stroke, respectively), as compared with healthy controls (HC), under the condition of perturbed proprioception. Eighteen LA-stroke and 18 HA-stroke survivors, as well as 18 gender- and age-matched HC, participated in this study. Postural sway variability (i.e. Root Mean Square (RMS) of the COP velocity) was measured for a duration of 180 s under two conditions: quiet standing and standing while predicting random virtual spheres to be avoided. Proprioceptive perturbation was simulated using bilateral Achilles tendon vibration at mid duration (60 s) for both conditions. The results showed that the HC were able to timely use visual anticipation to reduce the postural sway variability induced by tendon vibration. However, marked delay in using such anticipation was observed in stroke participants, especially in the HA-stroke group, as indicated by a significant decrease in the RMS of the COP velocity late in the vibration phase. This is the first study to consider the effect of anxiety while comparing sensory reweighting between stroke and healthy participants. The results indicated that chronic stroke survivors, particularly those with HA, could not efficiently use sensory reweighting to maintain balance in sensory conflicting conditions, which may subject them to loosing balance and/or falling. These findings are critical for future assessment and planning of rehabilitation interventions and balance in chronic stroke survivors.

Accommodative insufficiency in a student population in Iran.

PURPOSE: To determine the prevalence of accommodative insufficiency (AI) and its relation with age, gender, and refractive errors in a college-age student population in Iran. METHODS: The present study was conducted cross-sectionally in 2017. All students had optometric tests including measurement of visual acuity, objective and subjective refraction, as well as binocular vision and accommodative examinations. Amplitude of accommodation was measured with the Donders' push-up method using the Royal Air Force (RAF) rule. Monocular accommodative facility was measured with ±2.00diopter flipper lenses. The accommodative response was tested using dynamic retinoscopy with the monocular estimation method (MEM). RESULTS: The prevalence of AI in the studied population was 4.07% (95% CI: 2.61-5.52). The rate was 6.04% (95% CI: 3.58-8.50) in females and 2.01% (95% CI: 0.53-3.48) in males, and logistic regression showed a significantly higher odds of AI in females (OR=3.14, 95% CI: 1.33-7.45, p-value=0.009). The prevalence of AI was 2.59% (95% CI: 0.55-7.56) in the 18-19-year-old age group and 4.08% (95% CI: 0.09-8.07) in the 24-25-year-old group (p-value=0.848). The prevalence of AI among emmetropic, myopic, and hyperopic individuals was 3.74% (95% CI: 1.88-5.61), 4.44% (95% CI: 2.07-6.81), and 5.26% (95% CI: 4.79-16.32), respectively (p-value=0.869). In the multiple regression model, only gender showed significant relationship with AI (Odds ratio=3.14, 95% CI: 1.33-7.45; p-values=0.009). CONCLUSION: The prevalence of AI in the present study is lower than the most prevalence rates reported in previous studies. In the present study, gender and AI showed a strong association, such that AI prevalence was significantly higher in females than males.

The Prevalence of Age-Related Eye Disease in an Elderly Population.

PURPOSE: To determine the prevalence of cataracts, age-related macular degeneration (AMD), glaucoma, and diabetic retinopathy (DR) in Iranians over the age of 54 years. METHODS: Through a cross-sectional study using randomized cluster sampling, 60 clusters were selected in Sari, a city in the North of Iran. In each cluster, 20 people over 54 years of age were chosen systematically and were invited to participate in the study. After enrollment, all participants had optometric and ophthalmologic exams including slit lamp biomicroscopy and fundoscopy. RESULTS: Of the 1185 selected persons, 937 (79.1%) participated in this study (age range 55-87 years). The prevalence of cataracts, AMD, glaucoma, and DR in at least one eye was 29.6% (95% confidence interval [CI] 26.6-32.5), 5.8% (95% CI: 4.3-7.3), 3.7% (95% CI: 2.5-5.0), and 2.7% (95% CI: 1.6-3.7), respectively. All prevalences significantly increased with aging. AMD was more prevalent in men (7.4%) than women (4.4%) (p = 0.054). Overall, 35.8% (95% CI: 32.7-38.8) of participants had at least one of the four conditions; this rate was 27.4% for the 55-59-year old age group and 52.4% for those over 75 years of age. CONCLUSION: Overall, 35.8% of the studied population had at least one of the four diseases. Cataracts, followed by AMD, are the most common age-related eye diseases in the Iranian population, and thus, precise planning along with enhanced diagnostic and therapeutic facilities are necessary.

The prevalence of convergence insufficiency in Iran: a population-based study.

PURPOSE: The aim was to determine the prevalence of convergence insufficiency and its relationship with age, gender and refractive error in a population-based study. METHODS: In this cross-sectional study, all residents over one year old in Mashhad city, in the north east of Iran, were sampled through random stratified cluster sampling. After selecting samples and their participation in the study, they all had eye examinations including the measurement of visual acuity, refraction, binocular vision assessment, including cover test, measurement of near point of convergence and fusional vergences and finally, slitlamp biomicroscopy. RESULTS: Of the 4,453 selected people, 3,132 participated in the study and finally, analyses were done with data from 2,219 individuals. The mean age of the participants was 30.5 ± 14.0 years (range: 10 to 69). The prevalence of convergence insufficiency in this study was 5.51 per cent (range: 4.51 to 6.52): 4.78 per cent (range: 3.11 to 6.45) in males and 5.86 per cent (range: 4.60 to 7.11) in females (p = 0.276). Convergence insufficiency prevalence in different age groups showed no significant linear trend; however, a significant increase was observed after the age of 60 years. The prevalence of myopia, emmetropia and hyperopia was respectively 12.1, 56.9 and 31 per cent in participants with convergence insufficiency and 15.9, 54.4 and 29.6 per cent in those without convergence insufficiency (p = 0.537). Multiple logistic regression models revealed no significant relationship between the prevalence of convergence insufficiency and age, gender or refractive errors. CONCLUSION: This study showed that the overall prevalence of convergence insufficiency in the Iranian population was 5.46 per cent, which is lower than that in the majority of previous studies. Convergence insufficiency prevalence had no significant change with age up to the age of 60 years but increased significantly after 60 years.

Binocular and Accommodative Characteristics in a Normal Population.

PURPOSE: To study binocular and accommodative characteristics and their associations with age and gender in an Iranian young adult population. METHODS: In this cross-sectional study, multistage cluster sampling was done from the students of Mashhad University of Medical Sciences. All participants had visual acuity, refraction, and cover tests followed by measurements of the near point of convergence (NPC), amplitude of accommodation (AA), monocular and binocular accommodative facility (MAF and BAF) using ±2.00 diopter (D) flipper lenses, and negative and positive relative accommodation (NRA and PRA). Near and distance fusional vergence reserves were measured using prism bar, and near associated phoria was assessed using the Mallett unit. RESULTS: The mean age of the participants was 22.5±4.4 years (range: 18-35 years). The binocular and accommodative characteristics and their means in the studied sample included: mean distance dissociated phoria: 1.15 exophoria±2.04 prism diopters (PD), near dissociated phoria: 5.02 exophoria±4.74 PD, near associated phoria: 0.55 base-in±1.02, gradient accommodative convergence/accommodation (AC/A) ratio: 4.66±1.59, NPC: 5.27±3.60 cm, MAF: 11.33±5.58 cpm, BAF: 8.84±4.47 cpm, NRA: 2.08±0.33 D, PRA:-2.92±0.76 D, and AA: 11.14±2.6 D. In the multiple regression model including age and gender, near exophoria was significantly higher in men and levels of near base-out-break and near base-out-recovery were higher in females. Distance exophoria, distance base-in-break, distance base-in-recovery, and NPC increased with age and near base-out-break, PRA, BAF, MAF, and AA significantly decreased with age. CONCLUSION: Studied indices in this study significantly differ from available guidelines and these differences must be considered when making diagnostic or therapeutic decisions. Certain indices can be affected by age and gender.

Comparative study of changes of corneal curvatures and uncorrected distance visual acuity prior to and after corneal collagen crosslinking: 1-year results.

BACKGROUND/PURPOSE: Keratoconus is the most common primary corneal ectatic disease and has considerable importance in public health. Corneal collagen crosslinking (CXL) is a procedure to mitigate progression of keratoconus and reduce demand for corneal transplantation. The aim of this study was to evaluate the effect of CXL on corneal topographic and uncorrected distance visual acuity (UDVA) by Oculus Pentacam in the 15-30-year-old population. METHODS: In this descriptive-analytic study, we enrolled 38 eyes of 27 patients suffering from progressive keratoconus who were candidates for CXL. UDVA and the anterior and posterior corneal curvatures assessed prior to and 12 months after CXL. Data were analyzed by the paired t test and p < 0.05 was considered significant. RESULTS: One year after the CXL, mean UDVA significantly improved 0.1 ± 0.25 logarithm of the minimal angle of resolution (p = 0.012). Changes for steep keratometry values, flat keratometry, and mean keratometry on the anterior corneal surface were statistically significant (all p < 0.005). However, the difference observed in maximum keratometry and astigmatism was not significant (p = 0.421 and p = 0.745, respectively). After 12 months, all four keratometry values on the posterior corneal surface had increased significantly (p < 0.005), while no significant change observed in astigmatism (p = 0.303). CONCLUSION: Corneal collagen crosslinking has been revealed as an effective and minimally invasive intervention for the treatment of progressive keratoconus that can improve UDVA.